Pressure sensor chip

ABSTRACT

A pressure sensor chip according to the present invention includes two static-pressure diaphragms ( 2, 3 ) formed by dividing an annular diaphragm arranged so as to surround a differential-pressure diaphragm ( 1 ). A reference pressure is applied to one surface of one static-pressure diaphragm ( 2 ), and a measurement pressure (Pa) for one surface of the differential-pressure diaphragm ( 1 ) is transmitted to the other surface of the static-pressure diaphragm ( 2 ) along a branched path. A reference pressure is applied to one surface of the other static-pressure diaphragm ( 3 ), and a measurement pressure (Pb) for the other surface of the differential-pressure diaphragm ( 1 ) is transmitted to the other surface of the static-pressure diaphragm ( 3 ) along a branched path. Accordingly, multiple differential-pressure measurement ranges can be provided.

TECHNICAL FIELD

The present invention relates to pressure sensor chips including asensor diaphragm that outputs a signal corresponding to the differencebetween pressures applied to one and the other surfaces of the sensordiaphragm. An example of such a pressure sensor chip includes a thinplate-shaped diaphragm, which is displaced when a pressure is appliedthereto, and a strain resistance gauge formed on the diaphragm. Thepressure sensor chip detects the pressure applied to the diaphragm onthe basis of a change in the resistance of the strain resistance gaugeformed on the diaphragm.

BACKGROUND ART

Differential pressure sensors including built-in pressure sensor chips,which include a sensor diaphragm that outputs a signal corresponding tothe difference between pressures applied to one and the other surfacesof the sensor diaphragm, have been used as industrial differentialpressure sensors.

Such a differential pressure sensor is structured so that measurementpressures applied to high-pressure-side and low-pressure-sidepressure-receiving diaphragms are transmitted to one and the othersurfaces of the sensor diaphragm by enclosed liquid that serves as apressure transmitting medium. Strain of the sensor diaphragm is detectedas, for example, a change in resistance of a strain resistance gauge,and the resistance change is converted into an electrical signal to beoutput.

A differential pressure/static pressure composite sensor is an exampleof a differential pressure sensor capable of measuring not only adifferential pressure but also a static pressure. The differentialpressure/static pressure composite sensor includes adifferential-pressure diaphragm formed in a central region of asubstrate and an annular static-pressure diaphragm that surrounds theouter periphery of the differential-pressure diaphragm (see, forexample, PTL 1). The differential pressure/static pressure compositesensor is capable of detecting not only a differential pressure but alsoa static pressure by transmitting a measurement pressure applied to oneor the other surface of the differential-pressure diaphragm to onesurface of the static-pressure diaphragm along a branched path andapplying a reference pressure to the other surface of thestatic-pressure diaphragm.

CITATION LIST Patent Literature

-   PTL 1: Japanese Unexamined Patent. Application Publication No.    2010-91384

SUMMARY OF INVENTION Technical Problem

The sensitivity and withstand pressure of this type of sensor aredetermined by the aspect ratios of the diaphragms, and thereforemultiple measurement ranges can be obtained by changing the aspectratios. Accordingly, in general, the above-described differentialpressure/static pressure composite sensor (multivariable differentialpressure/static pressure sensor) can be realized by mounting diaphragmshaving different aspect ratios, that is, different ranges, on a singlechip. However, in this type of sensor, it is difficult to providemultiple differential-pressure measurement ranges, and multi-rangedifferential pressure sensors have not yet been realized.

An object of the present invention is to provide a pressure sensor chiphaving multiple differential-pressure measurement ranges.

Solution to Problem

A pressure sensor chip according to the present invention includes asubstrate; a sensor diaphragm of a first type that is formed in acentral region of the substrate and that outputs a signal correspondingto a difference between pressures applied to one surface and the othersurface thereof; sensor diaphragms of second and third types that areformed on the substrate so as to be apart from the sensor diaphragm ofthe first type, each of the sensor diaphragms of second and third typesoutputting a signal corresponding to a difference between pressuresapplied to one surface and the other surface thereof; first and secondholding members that are bonded to one surface and the other surface ofthe substrate in such a manner that peripheral portions of the first andsecond holding members face each other with the sensor diaphragms of thesecond and third types disposed therebetween; a first pressureintroduction hole provided in the first holding member to transmit afirst measurement pressure to the one surface of the sensor diaphragm ofthe first type; a second pressure introduction hole provided in thesecond holding member to transmit a second measurement pressure to theother surface of the sensor diaphragm of the first type; a first recessprovided in the first holding member to prevent the sensor diaphragm ofthe first type from being excessively displaced when an excessivepressure is applied to the sensor diaphragm of the first type; a secondrecess provided in the second holding member to prevent the sensordiaphragm of the first type from being excessively displaced when anexcessive pressure is applied to the sensor diaphragm of the first type;a first chamber provided in a peripheral portion of the first holdingmember as a space that faces the one surface of the sensor diaphragm ofthe second type; a second chamber provided in a peripheral portion ofthe second holding member as a space that faces the other surface of thesensor diaphragm of the second type; a third chamber provided in theperipheral portion of the first holding member as a space that faces theone surface of the sensor diaphragm of the third type; and a fourthchamber provided in the peripheral portion of the second holding memberas a space that faces the other surface of the sensor diaphragm of thethird type. The first measurement pressure for the one surface of thesensor diaphragm of the first type is transmitted to one of the firstchamber and the second chamber. A pressure in the other of the firstchamber and the second chamber is set to a reference pressure. Thesecond measurement pressure for the other surface of the sensordiaphragm of the first type is transmitted to one of the third chamberand the fourth chamber. A pressure in the other of the third chamber andthe fourth chamber is set to a reference pressure.

Advantageous Effects of Invention

According to the present invention, multiple differential-pressuremeasurement ranges can be provided by outputting a pressure differenceobtained by the sensor diaphragm of the first type as a low-rangedifferential pressure and the difference between a static pressureobtained by the sensor diaphragm of the second type and a staticpressure obtained by the sensor diaphragm of the third type as ahigh-range differential pressure.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram illustrating a pressure sensor chipaccording to a first embodiment of the present invention (Embodiment 1).

FIG. 2 is a diagram illustrating an example of the arrangement of adifferential-pressure diaphragm and static-pressure diaphragms in asubstrate of the pressure sensor chip according to Embodiment 1.

FIG. 3 is a plan view illustrating the shape of a plurality ofprotrusions that are discretely formed in non-bonding regions providedin stopper members included in the pressure sensor chip according toEmbodiment 1.

FIG. 4 is a plan view illustrating another example of the shape of aplurality of protrusions that are discretely formed in the non-bondingregions provided in the stopper members included in the pressure sensorchip according to Embodiment 1.

FIG. 5 is a diagram illustrating an arithmetic processing unit thatdetermines the difference between a static pressure obtained by a firststatic-pressure diaphragm and a static pressure obtained by a secondstatic-pressure diaphragm in the pressure sensor chip according toEmbodiment 1.

FIG. 6 is a diagram illustrating the state after thedifferential-pressure diaphragm has come into contact with the bottom ofa recess in a stopper member included in the pressure sensor chipaccording to Embodiment 1.

FIG. 7 is a schematic diagram illustrating a pressure sensor chipaccording to a second embodiment of the present invention (Embodiment2).

FIG. 8 is a diagram illustrating an example in which annular groovesformed in stopper members included in the pressure sensor chip accordingto Embodiment 2 are slit-shaped (has a rectangular cross section).

FIG. 9 is a diagram illustrating an example in which annular groovesformed in stopper members included in the pressure sensor chip accordingto Embodiment 2 are shaped such that a groove larger than a semicirculargroove and a groove smaller than a semicircular groove are shifted fromeach other.

FIG. 10 is a diagram illustrating the state after adifferential-pressure diaphragm has come into contact with the bottom ofa recess in a stopper member included in the pressure sensor chipaccording to Embodiment 2.

FIG. 11 is a schematic diagram illustrating a pressure sensor chipaccording to a third embodiment of the present invention (Embodiment 3).

FIG. 12 is a schematic diagram illustrating a pressure sensor chipaccording to a fourth embodiment of the present invention (Embodiment4).

FIG. 13 is a diagram illustrating another exemplary structure of firstand second static-pressure diaphragms.

FIG. 14 is a diagram illustrating another exemplary structure of firstand second static-pressure diaphragms.

FIG. 15 is a schematic diagram illustrating a pressure sensor chipaccording to a fifth embodiment of the present invention (Embodiment 5).

DESCRIPTION OF EMBODIMENTS

A pressure sensor chip according to the present invention will now bedescribed.

A pressure sensor chip according to the present invention includes asubstrate; a sensor diaphragm of a first type that is formed in acentral region of the substrate and that outputs a signal correspondingto a difference between pressures applied to one surface and the othersurface of the sensor diaphragm of the first type; sensor diaphragms ofsecond and third types that are formed on the substrate so as to beapart from the sensor diaphragm of the first type, each of the sensordiaphragms of second and third types outputting a signal correspondingto a difference between pressures applied to one surface and the othersurface thereof; first and second holding members that are bonded to onesurface and the other surface of the substrate in such a manner thatperipheral portions of the first and second holding members face eachother with the sensor diaphragms of the second and third types disposedtherebetween; a first pressure introduction hole provided in the firstholding member to transmit a first measurement pressure to the onesurface of the sensor diaphragm of the first type; a second pressureintroduction hole provided in the second holding member to transmit asecond measurement pressure to the other surface of the sensor diaphragmof the first type; a first recess provided in the first holding memberto prevent the sensor diaphragm of the first type from being excessivelydisplaced when an excessive pressure is applied to the sensor diaphragmof the first type; a second recess provided in the second holding memberto prevent the sensor diaphragm of the first type from being excessivelydisplaced when an excessive pressure is applied to the sensor diaphragmof the first type; a first chamber provided in a peripheral portion ofthe first holding member as a space that faces the one surface of thesensor diaphragm of the second type; a second chamber provided in aperipheral portion of the second holding member as a space that facesthe other surface of the sensor diaphragm of the second type; a thirdchamber provided in the peripheral portion of the first holding memberas a space that faces the one surface of the sensor diaphragm of thethird type; and a fourth chamber provided in the peripheral portion ofthe second holding member as a space that faces the other surface of thesensor diaphragm of the third type. The first measurement pressure forthe one surface of the sensor diaphragm of the first type is transmittedto one of the first chamber and the second chamber. A pressure in theother of the first chamber and the second chamber is set to a referencepressure. The second measurement pressure for the other surface of thesensor diaphragm of the first type is transmitted to one of the thirdchamber and the fourth chamber. A pressure in the other of the thirdchamber and the fourth chamber is set to a reference pressure.

In the pressure sensor chip according to the present invention, thefirst measurement pressure is transmitted to the one surface of thesensor diaphragm of the first type, and the second measurement pressureis transmitted to the other surface of the sensor diaphragm of the firsttype. Accordingly, the sensor diaphragm of the first type outputs asignal corresponding to the difference between the first measurementpressure and the second measurement pressure. The first measurementpressure for the one surface of the sensor diaphragm of the first typeis transmitted to one of the one surface and the other surface of thesensor diaphragm of the second type, and the reference pressure isapplied to the other of the one surface and the other surface of thesensor diaphragm of the second type. Accordingly, the sensor diaphragmof the second type outputs a signal corresponding to the differencebetween the first measurement pressure and the reference pressure. Thesecond measurement pressure for the other surface of the sensordiaphragm of the first type is transmitted to one of the one surface andthe other surface of the sensor diaphragm of the third type, and thereference pressure is applied to the other of the one surface and theother surface of the sensor diaphragm of the third type. Accordingly,the sensor diaphragm of the third type outputs a signal corresponding tothe difference between the second measurement pressure and the referencepressure.

In the pressure sensor chip according to the present invention, thesensor diaphragm of the first type constitutes a differential pressuresensor that detects the difference between the first measurementpressure and the second measurement pressure, the sensor diaphragm ofthe second type constitutes a static pressure sensor that detects thefirst measurement pressure as a static pressure, and the sensordiaphragm of the third type constitutes a static pressure sensor thatdetects the second measurement pressure as a static pressure. When, forexample, the first measurement pressure is higher than the secondmeasurement pressure, the sensor diaphragm of the second typeconstitutes a high-pressure-side static pressure sensor and the sensordiaphragm of the third type constitutes a low-pressure-side staticpressure sensor. When, for example, the second measurement pressure ishigher than the first measurement pressure, the sensor diaphragm of thesecond type constitutes a low-pressure-side static pressure sensor andthe sensor diaphragm of the third type constitutes a high-pressure-sidestatic pressure sensor.

In the pressure sensor chip according to the present invention, in thecase where the pressure sensitivities of the sensor diaphragms of thesecond and third types are lower than the pressure sensitivity of thesensor diaphragm of the first type, the pressure difference obtained bythe sensor diaphragm of the first type can be output as a low-rangedifferential pressure, and the difference between the static pressureobtained by the sensor diaphragm of the second type and the staticpressure obtained by the sensor diaphragm of the third type can beoutput as a high-range differential pressure. More specifically, when alow differential pressure is applied, the differential pressure can beaccurately measured by the sensor diaphragm of the first type. When ahigh differential pressure is applied, the differential pressure can beaccurately measured by the sensor diaphragms of the second and thirdtypes. Thus, multiple differential-pressure measurement ranges can beprovided.

Although an excessive pressure is applied to the sensor diaphragm of thefirst type when a high differential pressure is applied, the sensordiaphragm of the first type does not break because the recesses forpreventing the sensor diaphragm of the first type from being excessivelydisplaced are formed in the first holding member and the second holdingmember.

Pressure sensor chips according to embodiments of the present inventionwill now be described in detail with reference to the drawings.

Embodiment 1

FIG. 1 is a schematic diagram illustrating a pressure sensor chipaccording to a first embodiment of the present invention (Embodiment 1).FIG. 1 illustrates a substrate 11-1, which serves as a base plate; firstand second stopper members 11-2 and 11-3, which are bonded together withthe substrate 11-1 interposed therebetween and which serve as holdingmembers; and first and second bases 11-4 and 11-5, which arerespectively bonded to the stopper members 11-2 and 11-3. The stoppermembers 11-2 and 11-3 and the bases 11-4 and 11-5 are made of, forexample, silicon or glass.

In this pressure sensor chip 11A, a differential-pressure diaphragm 1,which serves as a sensor diaphragm of a first type, a firststatic-pressure diaphragm 2, which serves as a sensor diaphragm of asecond type, and a second static-pressure diaphragm 3, which serves as asensor diaphragm of a third type, are formed in the substrate 11-1 bydry etching.

FIG. 2 illustrates an example of the arrangement of thedifferential-pressure diaphragm 1 and the static-pressure diaphragms 2and 3 in the substrate 11-1. In this example, the differential-pressurediaphragm 1, which is circular, is provided in a central region of thesubstrate 11-1, and the static-pressure diaphragms 2 and 3, which aresemicircular-strip-shaped (C-shaped), are arranged so as to face eachother with the differential-pressure diaphragm 1 disposed therebetween.

More specifically, diaphragms that form an annular shape are arranged soas to surround the differential-pressure diaphragm 1, one of thediaphragms serving as the static-pressure diaphragm 2 and the other asthe static-pressure diaphragm 3. In the present embodiment, the areas ofpressure-receiving surfaces of the static-pressure diaphragms 2 and 3are smaller than the area of pressure-receiving surfaces of thedifferential-pressure diaphragm 1. Accordingly, the pressuresensitivities of the static-pressure diaphragms 2 and 3 are lower thanthe pressure sensitivity of the differential-pressure diaphragm 1.

The substrate 11-1, in which the differential-pressure diaphragm 1 andthe static-pressure diaphragms 2 and 3 are provided, is disposed betweena stopper member 11-2 and a stopper member 11-3. More specifically, thedifferential-pressure diaphragm 1 is formed between one and the othersurfaces of the substrate 11-1 in the central region of the substrate11-1, and the static-pressure diaphragms 2 and 3 are formed between theone and the other surfaces of the substrate 11-1 so as to face eachother with a peripheral portion of the differential-pressure diaphragm 1disposed therebetween. The stopper member 11-2 is bonded to the onesurface of the substrate 11-1, and the stopper member 11-3 is bonded tothe other surface of the stopper member 11-3.

A chamber 4, which is a space (semicircular-strip-shaped space) thatfaces one surface of the static-pressure diaphragm 2, and a chamber 6,which is a space (semicircular-strip-shaped space) that faces onesurface of the static-pressure diaphragm 3, are provided in a peripheralportion of the stopper member 11-2. A chamber which is a space(semicircular-strip-shaped space) that faces the other surface of thestatic-pressure diaphragm 2, and a chamber 7, which is a space(semicircular-strip-shaped space) that faces the other surface of thestatic-pressure diaphragm 3, are provided in a peripheral portion of thestopper member 11-3. Hereinafter, the chamber 4 provided in the stoppermember 11-2 is referred to as a first chamber, the chamber 5 provided inthe stopper member 11-3 is referred to as a second chamber, the chamber6 provided in the stopper member 11-2 is referred to as a third chamber,and the chamber 7 provided in the stopper member 11-3 is referred to asa fourth chamber.

In the present embodiment, the pressures in the second chamber 5 and thethird chamber 6 are set to a reference pressure, for example, the vacuumpressure or atmospheric pressure. The width of the one surface of thestatic-pressure diaphragm 2 that faces the first chamber 4, that is, thewidth W1 of the first chamber 4 that faces the one surface of thestatic-pressure diaphragm 2, is greater than the width of the othersurface of the static-pressure diaphragm 2 that faces the second chamber5, that is, the width W2 of the second chamber 5 that faces the othersurface of the static-pressure diaphragm 2. The width of the othersurface of the static-pressure diaphragm 3 that faces the fourth chamber7, that is, the width W3 of the fourth chamber 7 that faces the othersurface of the static-pressure diaphragm 3, is greater than the width ofthe one surface of the static-pressure diaphragm 3 that faces the thirdchamber 6, that is, the width W4 of the third chamber 6 that faces theone surface of the static-pressure diaphragm 3.

A chamber 8, which is a space that faces one surface of thedifferential-pressure diaphragm 1, is provided in a central portion ofthe stopper member 11-2, and a chamber 9, which is a space that facesthe other surface of the differential-pressure diaphragm 1, is providedin the central portion of the stopper member 11-3. The chambers 8 and 9are the spaces formed of recesses 11-2 a and 11-3 a that respectivelyface the one and the other surfaces of the differential-pressurediaphragm 1. The recesses 11-2 a and 11-3 a have curved surfaces(non-spherical surfaces) that follow the differential-pressure diaphragm1 in the displaced state. In the chambers 8 and 9, pressure introducingholes (pressure introduction holes) 11-2 b and 11-3 b are formed at thebottom portions of the recesses 11-2 a and 11-3 a. In addition, pressureintroducing holes (pressure introduction holes) 11-4 a and 11-5 a areformed in the bases 11-4 and 11-5, respectively, at positionscorresponding to the positions of the pressure introduction holes 11-2 band 11-3 b in the stopper members 11-2 and 11-3.

In the pressure sensor chip 11A, the stopper member 11-2 has anon-bonding region SA1 provided therein. The non-bonding region SA1 isconnected to the periphery of the pressure introduction hole 11-2 b. Thenon-bonding region SA1 is provided as a region in which a first surfacePL1 and a second surface PL2 are separated from each other and face eachother along a portion of a plane PL that is parallel to the one surfaceof the substrate 11-1.

As illustrated in FIG. 3, a plurality of protrusions (columns) 12 arediscretely formed on at least one of the first and second surfaces PL1and PL2 that face each other in the non-bonding region SA1 (firstsurface PL1 in this example). Passages (grooves) 13 between theprotrusions 12 serve as channels between the periphery of the pressureintroduction hole 11-2 b and a peripheral edge 14 of the non-bondingregion SA1. Although the protrusions 12 have the shape of a circularcolumn in this example, the protrusions 12 may instead have the shape ofa hexagonal column as illustrated in FIG. 4.

In this example, the stopper member 11-2 is divided into two portionsalong the plane PL parallel to the one surface of the substrate 11-1.More specifically, the stopper member 11-2 is formed by bonding the twoportions, which are a stopper member 11-21 and a stopper member 11-22,in a region SB1 excluding the non-bonding region SA1 along the plane PLincluding the non-bonding region SA1. Thus, the plane PL parallel to theone surface of the substrate 11-1 is divided into the non-bonding regionSA1, which is connected to the periphery of the pressure introductionhole 11-2 b, and the bonding region SE1, which is not connected to theperiphery of the pressure introduction hole 11-2 b.

Similar to the stopper member 11-2, the stopper member 11-3 also has anon-bonding region SA2 provided therein. The non-bonding region SA2 isconnected to the periphery of the pressure introduction hole 11-3 b. Thenon-bonding region SA2 is provided as a region in which a first surfacePL1 and a second surface PL2 are separated from each other and face eachother along a portion of a plane PL that is parallel to the othersurface of the substrate 11-1.

Similar to the non-bonding region SA1 in the stopper member 11-2, aplurality of protrusions (columns) 12 are discretely formed on at leastone of the first and second surfaces PL1 and PL2 that face each other inthe non-bonding region SA2 (first surface PL1 in this example). Passages(grooves) 13 between the protrusions 12 serve as channels between theperiphery of the pressure introduction hole 11-3 b and a peripheral edge14 of the non-bonding region SA2. Although the protrusions 12 have theshape of a circular column in this example, the protrusions 12 mayinstead have the shape of a hexagonal column.

In this example, the stopper member 11-3 is divided into two portionsalong the plane PL parallel to the other surface of the substrate 11-1.More specifically, the stopper member 11-3 is formed by bonding the twoportions, which are a stopper member 11-31 and a stopper member 11-32,in a region SB2 excluding the non-bonding region SA2 along the plane PLincluding the non-bonding region SA2. Thus, the plane PL parallel to theother surface of the substrate 11-1 is divided into the non-bondingregion SA2, which is connected to the periphery of the pressureintroduction hole 11-3 b, and the bonding region SB2, which is notconnected to the periphery of the pressure introduction hole 11-3 b.

In the stopper member 11-2, the first chamber 4 and the third chamber 6are formed in the stopper member 11-21 together with the recess 11-2 a.A pressure introducing hole (pressure introduction hole) 11-2 c isformed between the first chamber 4 and the non-bonding region SA1. Inthe stopper member 11-3, the second chamber 5 and the fourth chamber 7are formed in the stopper member 11-31 together with the recess 11-3 a.A pressure introducing hole (pressure introduction hole) 11-3 c isformed between the fourth chamber 7 and the non-bonding region SA2.

In the pressure sensor chip 11A, a measurement pressure Pa istransmitted into the chamber 8 through the pressure introduction hole11-2 b in the stopper member 11-2, and a measurement pressure Pb istransmitted into the chamber 9 through the pressure introduction hole11-3 b provided in the stopper member 11-3. Thus, thedifferential-pressure diaphragm 1 is displaced by an amountcorresponding to the difference between the measurement pressure Patransmitted into the chamber 8 and the measurement pressure Pbtransmitted into the chamber 9. The stress generated at an edge portionof the differential-pressure diaphragm 1 due to the displacement of thedifferential-pressure diaphragm 1 is detected as a differential pressureΔP based on changes in the resistances of piezoresistors (not shown)provided on the edge portion of the differential-pressure diaphragm 1.

In the pressure sensor chip 11A, the measurement pressure Pa is alsotransmitted to the non-bonding region SA1 provided in the stopper member11-2 through the pressure introduction hole 11-2 b, and the measurementpressure Pa that has been transmitted to the non-bonding region SA1 istransmitted to the first chamber 4, which faces the one surface of thestatic-pressure diaphragm 2, through the pressure introduction hole 11-2c. The pressure in the second chamber 5, which faces the other surfaceof the static-pressure diaphragm 2, is set to a reference pressure, forexample, the vacuum pressure or atmospheric pressure. Accordingly, thestatic-pressure diaphragm 2 is displaced by an amount corresponding tothe difference between the measurement pressure Pa transmitted into thefirst chamber 4 and the reference pressure in the second chamber 5. Thestress generated at an edge portion of the static-pressure diaphragm 2due to the displacement of the static-pressure diaphragm 2 is detectedas a static pressure Pa based on changes in the resistances ofpiezoresistors ra1 to ra4 illustrated in FIG. 2, which are provided onthe edge portion of the static-pressure diaphragm 2.

In the pressure sensor chip 11A, the measurement pressure Pb is alsotransmitted to the non-bonding region SA2 provided in the stopper member11-3 through the pressure introduction hole 11-3 b, and the measurementpressure Pb that has been transmitted to the non-bonding region SA2 istransmitted to the fourth chamber 7, which faces the other surface ofthe static-pressure diaphragm 3, through the pressure introduction hole11-3 c. The pressure in the third chamber 6, which faces the one surfaceof the static-pressure diaphragm 3, is set to a reference pressure, forexample, the vacuum pressure or atmospheric pressure. Accordingly, thestatic-pressure diaphragm 3 is displaced by an amount corresponding tothe difference between the measurement pressure Pb transmitted into thefourth chamber 7 and the reference pressure in the third chamber 6. Thestress generated at an edge portion of the static-pressure diaphragm 3due to the displacement of the static-pressure diaphragm 3 is detectedas a static pressure Ph based on changes in the resistances ofpiezoresistors rb1 to rb4 illustrated in FIG. 2, which are provided onthe edge portion of the static-pressure diaphragm 3.

In the present embodiment, the pressure sensitivities of thestatic-pressure diaphragms 2 and 3 are lower than the pressuresensitivity of the differential-pressure diaphragm 1. Therefore, when alow differential pressure is applied, although the differential-pressurediaphragm 1 is displaced by an amount corresponding to the differentialpressure ΔP, the static-pressure diaphragms 2 and 3 are not displaced byamounts corresponding to the static pressures Pa and Pb. When a highdifferential pressure is applied, the differential-pressure diaphragm 1is prevented from being excessively displaced by the recesses 11-2 a and11-3 a in the stopper members 11-2 and 11-3, so that thedifferential-pressure diaphragm 1 is not displaced by an amountcorresponding to the differential pressure ΔP. However, thestatic-pressure diaphragms 2 and 3 are displaced by amountscorresponding to the static pressures Pa and Pb.

Referring to FIG. 5, in the present embodiment, an arithmetic processingunit 10 is provided to determine the pressure difference between thestatic pressure Pa obtained by the first static-pressure diaphragm 2 andthe static pressure Pb obtained by the second static-pressure diaphragm3 as ΔPab=|Pa−Pb|. The pressure difference ΔPab between the staticpressure Pa and the static pressure Pb obtained by the arithmeticprocessing unit 10 is output as a high-range differential pressureΔP_(H), and the pressure difference ΔP obtained by thedifferential-pressure diaphragm 1 is output as a low-range differentialpressure ΔP_(L).

Accordingly, when a low differential pressure is applied, thedifferential-pressure diaphragm (sensor diaphragm of the first type) 1is used to accurately measure the difference between the pressuresapplied to the differential-pressure diaphragm 1. When a highdifferential pressure is applied, the first static-pressure diaphragm(sensor diaphragm of the second type) 2 and the second static-pressurediaphragm (sensor diaphragm of the third type) 3 are used to accuratelymeasure the difference between the pressures applied to the firststatic-pressure diaphragm 2 and the second static-pressure diaphragm 3.Thus, multiple differential-pressure measurement ranges are provided.

Although an excessive pressure is applied to the differential-pressurediaphragm 1 when a high differential pressure is applied, thedifferential-pressure diaphragm 1 does not break because the recesses11-2 a and 11-3 a in the stopper members 11-2 and 11-3 prevent thedifferential-pressure diaphragm 1 from being excessively displaced.

For example, assume that, in the pressure sensor chip 11A, themeasurement pressure Pb is the high-pressure-side measurement pressureand the measurement pressure Pa is the low-pressure-side measurementpressure. In this case, when the high-pressure-side measurement pressurePb is applied to the other surface of the differential-pressurediaphragm 1, the differential-pressure diaphragm 1 is bent toward thestopper member 11-2. At this time, the stopper member 11-3 receives aforce in a direction opposite to the direction in which thedifferential-pressure diaphragm 1 is bent, and tries to form an openingat a diaphragm edge, for example, at locations indicated by points G inFIG. 1. In the following description, the direction in which thedifferential-pressure diaphragm 1 is bent in FIG. 1 is referred to asthe upward direction, and the direction opposite to the direction inwhich the differential-pressure diaphragm 1 is bent is referred to asthe downward direction.

In this case, in the present embodiment, since the measurement pressurePb is transmitted to the non-bonding region SA2 provided in the stoppermember 11-3 through the pressure introduction hole 11-3 b, thenon-bonding region SA2 provides a pressure-receiving surface thatreceives the measurement pressure Pb and reduces the downward forceapplied to the stopper member 11-3, so that no opening is formed at thediaphragm edge. Accordingly, the stress generated because thedifferential-pressure diaphragm 1 is restrained is reduced, and stressconcentration does not occur at the diaphragm edge.

In the pressure sensor chip 11A, the non-bonding region SA2 exerts agreater effect when the excessive pressure increases after thedifferential-pressure diaphragm 1 has come into contact with the bottomof the recess 11-2 a in the stopper member 11-2. This will be describedin detail with reference to FIG. 6.

FIG. 6 illustrates the state after the differential-pressure diaphragm 1has come into contact with the bottom of the recess 11-2 a in thestopper member 11-2. When an excessive pressure is applied to the othersurface of the differential-pressure diaphragm 1, thedifferential-pressure diaphragm 1 is bent toward the stopper member11-2, and comes into contact with the bottom of the recess 11-2 a in thestopper member 11-2. When the excessive pressure increases after thedifferential-pressure diaphragm 1 has come into contact with the bottomof the recess 11-2 a, the stopper member 11-3 is deformed by thedownward force applied to the stopper member 11-3, and tries to form anopening at the diaphragm edge.

In this case, according to the present embodiment, the excessivepressure is also transmitted to the non-bonding region SA2, which isprovided in the stopper member 11-3, through the pressure introductionhole 11-3 b uniformly along the passages 13 between the protrusions 12.Accordingly, the non-bonding region SA2 provides a pressure-receivingsurface that receives the excessive pressure, and applies an upwardforce to the stopper member 11-31. Owing to this force, deformation ofthe stopper member 11-31 is suppressed, or the stopper member 11-31 isdeformed in the opposite direction. In the example illustrated in FIG.6, the stopper member 11-31 is deformed in the upward direction so as tofollow the upward deformation of the differential-pressure diaphragm 1.

Accordingly, even when the excessive pressure increases after thedifferential-pressure diaphragm 1 has come into contact with the bottomof the recess 11-2 a in the stopper member 11-2, no opening is formed atthe diaphragm edge, and stress concentration does not occur at thediaphragm edge. Therefore, an expected withstand pressure can beobtained. Thus, the differential-pressure diaphragm 1 is prevented frombeing broken during the measurement of the high-range differentialpressure ΔP_(H) by the static-pressure diaphragms 2 and 3.

In the present embodiment, the area of the non-bonding region SA2provided in the stopper member 11-3, that is, the pressure-receivingarea in the stopper member 11-3, is preferably sufficiently greater thanthe pressure-receiving area of the recess 11-3 a in the stopper member11-3 so that the deformation of the stopper member 11-3 in the downwarddirection can be suppressed or the stopper member 11-3 can be deformedin the opposite direction.

In the present embodiment, the protrusions 12 are discretely formed onthe first surface PL1 in the non-bonding region SA2 provided in thestopper member 11-3. However, the protrusions 12 may instead bediscretely formed on the second surface PL2. Alternatively, theprotrusions 12 may instead be formed on both the first surface PL1 andthe second surface PL2.

In the above-described example, it is assumed that the measurementpressure Pb is the high-pressure-side measurement pressure and themeasurement pressure Pa is the low-pressure-side measurement pressure.In the case where the measurement pressure Pa is the high-pressure-sidemeasurement pressure and the measurement pressure Pb is thelow-pressure-side measurement pressure, the non-bonding region SA1 inthe stopper member 11-2 serves the same function as the function of thenon-bonding region SA2 in the stopper member 11-3. Accordingly, anoperation similar to the above-described operation is performed.

In the present embodiment, since the protrusions 12 are discretelyformed on the first surface PL1 in the each of non-bonding regions SA1and SA2 provided in the stopper members 11-2 and 11-3, and since thepassages 13 between the protrusions 12 serve as channels between theperipheries of the pressure introduction holes 11-2 b and 11-3 b and theperipheral edges 14 of the non-bonding regions SA1 and SA2, a commonlyused pressure transmitting medium, such as oil, can be easily enclosed.Furthermore, by reducing the transmission resistance of the pressuretransmitting medium to be enclosed, the influence of malfunction due toa difference in transmission speed can be eliminated. With regard to anapplication of pressure from the opposite side, sufficient withstandpressure can be ensured by optimizing the area of the protrusions 12.

Embodiment 2

FIG. 7 is a schematic diagram illustrating a pressure sensor chipaccording to a second embodiment of the present invention (Embodiment2). A pressure sensor chip 11E according to Embodiment 2 includesannular grooves 11-2 d and 11-3 d, which are respectively formed in thestopper members 11-2 and 11-3. The annular grooves 11-2 d and 11-3 d arerespectively connected to the non-bonding regions SA1 and SA2 and areformed so as to project in the thickness direction of the stoppermembers 11-2 and 11-3. The annular grooves 11-2 d and 11-3 d arecontinuous grooves that are not divided at discrete locations, and thecross sections thereof preferably have a large diameter.

In the example illustrated in FIG. 7, the cross sections of the annulargrooves 11-2 d and 11-3 d along a plane perpendicular to the non-bondingregions SA1 and SA2 are circular. However, the cross-sectional shapesare not limited to circular, and may instead be, for example, aslit-shape (rectangular) as illustrated in FIG. 8, or a shapeillustrated in FIG. 9 in which a major-arc-shaped or semicircular grooveand a minor-arc-shaped or semicircular groove are combined such that thegrooves are shifted from each other.

FIG. 10 illustrates the state after the differential-pressure diaphragm1 has come into contact with the bottom of the recess 11-2 a in thestopper member 11-2 included in the pressure sensor chip 11B illustratedin FIG. 7. When the annular grooves 11-2 d and 11-3 d are formed, thestress is distributed in the annular grooves 11-2 d and 11-3 d.Therefore, the withstand pressure can be further increased.

Embodiment 3

FIG. 11 is a schematic diagram illustrating a pressure sensor chipaccording to a third embodiment of the present invention (Embodiment 3).In a pressure sensor chip 11C according to Embodiment 3, a pressureintroduction hole 11-3 c, which is connected to the non-bonding regionSA2 in the stopper member 11-3, is connected to the third chamber 6,which faces the one surface of the static-pressure diaphragm 3, insteadof the fourth chamber 7. The pressure in the fourth chamber 7, whichfaces the other surface of the static-pressure diaphragm 3, is set a toreference pressure, for example, the vacuum pressure or atmosphericpressure.

As illustrated in FIG. 11, the width of the one surface of thestatic-pressure diaphragm 3 that faces the third chamber 6, that is, thewidth W4 of the third chamber 6 that faces the one surface of thestatic-pressure diaphragm 3, is greater than the width of the othersurface of the static-pressure diaphragm 3 that faces the fourth chamber7, that is, the width W3 of the fourth chamber 7 that faces the othersurface of the static-pressure diaphragm 3.

In the pressure sensor chip 11C, the measurement pressure Pb istransmitted to the non-bonding region SA2 provided in the stopper member11-3 through the pressure introduction hole 11-3 b. The measurementpressure Pb that has been transmitted to the non-bonding region SA2enters the stopper member 11-21, and is transmitted to the third chamber6, which faces the one surface of the static-pressure diaphragm 3,through the pressure introduction hole 11-3 c. The pressure in thefourth chamber 7, which faces the other surface of the static-pressurediaphragm 3, is set to a reference pressure, for example, the vacuumpressure or atmospheric pressure.

Accordingly, the static-pressure diaphragm 3 is displaced by an amountcorresponding to the difference between the measurement pressure Pbtransmitted into the third chamber 6 and the reference pressure in thefourth chamber 7. The stress generated at an edge portion of thestatic-pressure diaphragm 3 due to the displacement of thestatic-pressure diaphragm 3 is detected as a static pressure Pb based onchanges in the resistances of piezoresistors provided on the edgeportion of the static-pressure diaphragm 3.

In this pressure sensor chip 11C, the measurement pressure Pb is appliedto the static-pressure diaphragm 3 in the same direction as thedirection in which the measurement pressure Pa is applied to thestatic-pressure diaphragm 2, and the static-pressure diaphragms 2 and 3are bent in the same direction on the substrate 11-1. Accordingly, thepressures are applied to the static-pressure diaphragms 2 and 3 underthe same conditions, and the measurement accuracy of the high-rangedifferential pressure ΔP_(H) can be increased.

Embodiment 4

FIG. 12 is a schematic diagram illustrating a pressure sensor chipaccording to a fourth embodiment of the present invention (Embodiment4). In a pressure sensor chip 11D according to Embodiment 4, which is amodification of the pressure sensor chip 11C according to Embodiment 3,the measurement pressures Pa and Pb are introduced in the samedirection.

In this example, the measurement pressure Pa and the measurementpressure Pb are introduced in the same direction. More specifically, inthe pressure sensor chip 11D according to Embodiment 4, a pressureintroduction hole 15, which is formed so as to extend through the base11-5, the stopper member 11-3, the substrate 11-1, and the stoppermember 11-2, is connected to the pressure introduction hole 11-2 b inthe stopper member 11-2 through the base 11-4. Thus, the measurementpressure Pa, which is introduced in the same direction as the directionin which the measurement pressure Pb is introduced, is transmitted tothe one surface of the differential-pressure diaphragm 1 and the onesurface of the static-pressure diaphragm 2.

In the above-described embodiments, the static-pressure diaphragms 2 and3 are semicircular-strip-shaped (for example, C-shaped). However, theshapes of the static-pressure diaphragms 2 and 3 are not limited tothis. For example, as illustrated in FIGS. 13 and 14, the firststatic-pressure diaphragm 2 may be formed of arc-shaped or rectangulardiaphragms 2-1 and 2-2 that face each other with thedifferential-pressure diaphragm 1 disposed therebetween, and the secondstatic-pressure diaphragm 3 may be formed of arc-shaped or rectangulardiaphragms 3-1 and 3-2 that face each other with thedifferential-pressure diaphragm 1 disposed therebetween at locationsshifted from the first static-pressure diaphragm 2 by 90 degrees.

Embodiment 5

FIG. 15 is a schematic diagram illustrating a pressure sensor chipaccording to a fifth embodiment of the present invention (Embodiment 5).

In Embodiments 1 to 4, the non-bonding regions SA1 and SA2 arerespectively provided in the stopper members 11-2 and 11-3, and themeasurement pressures Pa and Pb are respectively transmitted to thestatic-pressure diaphragms 2 and 3 through the non-bonding regions SA1and SA2 along branched paths. However, as in a pressure sensor chip 11Eaccording to Embodiment 5 illustrated in FIG. 15, the paths along whichthe measurement pressures Pa and Pb are transmitted to thestatic-pressure diaphragms 2 and 3 may be branched outside the pressuresensor chip 11E.

In the above-described embodiments, a plurality of protrusions (columns)12 are discretely formed in the non-bonding regions SA1 and SA2 providedin the stopper members 11-2 and 11-3, and passages (grooves) 13 betweenthe protrusions 12 serve as channels between the peripheries of thepressure introduction holes 11-2 b and 11-3 b and the peripheral edges14 of the non-bonding regions SA1 and SA2. However, the channels are notlimited to those defined by the discretely formed protrusions 12, andsimple slit-shaped gaps may instead be used as the channels.

Other Embodiments

Although the present invention has been described by referring toembodiments, the present invention is not limited to the above-describedembodiments. Various modifications that are understandable by a personskilled in the art can be made on the structure and details of thepresent invention within the technical idea of the present invention. Inaddition, the embodiments may be implemented in any combination unlessthey contradict each other.

INDUSTRIAL APPLICABILITY

The pressure sensor chip according to the present invention isapplicable to various uses, and may be used as, for example, anindustrial differential pressure sensor.

REFERENCE SIGNS LIST

1 differential-pressure diaphragm, 2 first static-pressure diaphragm, 3second static-pressure diaphragm, 4 first chamber, 5 second chamber, 6third chamber, 7 fourth chamber, 10 arithmetic processing unit, 11-1substrate, 11-2 (11-21, 11-22), 11-3 (11-31, 11-32) stopper member, 11-2a, 11-3 a recess, 11-2 b, 11-11-3 b, 11-3 c pressure introduction hole,11-4, 11-5 base, 12 protrusion (column), 13 passage (groove), 14peripheral edge, SA non-bonding region, SB bonding region, ra1 to ra4,rb1 to rb4 piezoresistor.

The invention claimed is:
 1. A pressure sensor chip comprising: asubstrate; a sensor diaphragm of a first type that is formed in acentral region of the substrate and that outputs a signal correspondingto a difference between pressures applied to one surface and the othersurface of the sensor diaphragm of the first type; sensor diaphragms ofsecond and third types that are formed on the substrate so as to beapart from the sensor diaphragm of the first type, each of the sensordiaphragms of second and third types outputting a signal correspondingto a difference between pressures applied to one surface and the othersurface thereof; first and second holding members that are bonded to onesurface and the other surface of the substrate in such a manner that thefirst and second holding members face each other with the sensordiaphragms of the second and third types disposed therebetween; a firstpressure introduction hole provided in the first holding member totransmit a first measurement pressure to the one surface of the sensordiaphragm of the first type; a second pressure introduction holeprovided in the second holding member to transmit a second measurementpressure to the other surface of the sensor diaphragm of the first type;a first recess provided in the first holding member to prevent thesensor diaphragm of the first type from being excessively displaced whenan excessive pressure is applied to the sensor diaphragm of the firsttype; a second recess provided in the second holding member to preventthe sensor diaphragm of the first type from being excessively displacedwhen an excessive pressure is applied to the sensor diaphragm of thefirst type; a first chamber provided in a peripheral portion of thefirst holding member as a space that faces the one surface of the sensordiaphragm of the second type; a second chamber provided in a peripheralportion of the second holding member as a space that faces the othersurface of the sensor diaphragm of the second type; a third chamberprovided in the peripheral portion of the first holding member as aspace that faces the one surface of the sensor diaphragm of the thirdtype; and a fourth chamber provided in the peripheral portion of thesecond holding member as a space that faces the other surface of thesensor diaphragm of the third type, wherein the first measurementpressure for the one surface of the sensor diaphragm of the first typeis transmitted to one of the first chamber and the second chamber,wherein a pressure in the other of the first chamber and the secondchamber is set to a reference pressure, wherein the second measurementpressure for the other surface of the sensor diaphragm of the first typeis transmitted to one of the third chamber and the fourth chamber, andwherein a pressure in the other of the third chamber and the fourthchamber is set to a reference pressure.
 2. The pressure sensor chipaccording to claim 1, wherein, when the first measurement pressure ishigher than the second measurement pressure, the sensor diaphragm of thesecond type constitutes a high-pressure-side static pressure sensor, andthe sensor diaphragm of the third type constitutes a low-pressure-sidestatic pressure sensor, and wherein, when the second measurementpressure is higher than the first measurement pressure, the sensordiaphragm of the second type constitutes a low-pressure-side staticpressure sensor, and the sensor diaphragm of the third type constitutesa high-pressure-side static pressure sensor.
 3. The pressure sensor chipaccording to claim 2, wherein a pressure difference obtained by thesensor diaphragm of the first type is output as a low-range differentialpressure, and wherein a difference between a static pressure obtained bythe sensor diaphragm of the second type and a static pressure obtainedby the sensor diaphragm of the third type is output as a high-rangedifferential pressure.
 4. The pressure sensor chip according to claim 1,wherein each of the sensor diaphragms of the second and third typesincludes a plurality of diaphragms.
 5. The pressure sensor chipaccording to claim 1, wherein pressure sensitivities of the sensordiaphragms of the second and third types are lower than a pressuresensitivity of the sensor diaphragm of the first type.
 6. The pressuresensor chip according to claim 1, wherein the sensor diaphragms of thesecond and third types are one and the other of diaphragms that areseparated from each other and arranged so as to surround a periphery ofthe sensor diaphragm of the first type in an annular shape.
 7. Thepressure sensor chip according to claim 1, wherein the first holdingmember includes a non-bonding region provided inside the first holdingmember and connected to a periphery of the first pressure introductionhole, wherein the non-bonding region in the first holding member is aregion in which a first surface and a second surface face each otheralong a portion of a plane parallel to the one surface of the substrate,wherein a plurality of protrusions are discretely formed on at least oneof the first surface and the second surface that face each other in thenon-bonding region in the first holding member, wherein passages betweenthe plurality of protrusions formed in the first holding member formchannels between the periphery of the first pressure introduction holeand a peripheral edge of the non-bonding region, wherein the secondholding member includes a non-bonding region provided inside the secondholding member and connected to a periphery of the second pressureintroduction hole, wherein the non-bonding region in the second holdingmember is a region in which a first surface and a second surface faceeach other along a portion of a plane parallel to the other surface ofthe substrate, wherein a plurality of protrusions are discretely formedon at least one of the first surface and the second surface that faceeach other in the non-bonding region in the second holding member, andwherein passages between the plurality of protrusions formed in thesecond holding member form channels between the periphery of the secondpressure introduction hole and a peripheral edge of the non-bondingregion.